The theme I use for my apps is just gtk4 (with gtk4 for gtk3) and Grandiance on wich I put the same color palette than the material you apps on my phone so the feel is consistent between devices
I can’t remember my icon pack rn, but I use and love the cursor pack from Mint as I am not a huge fan of the mouse stem. (The one from Peepin is also really great)
If I understood correctly, Docker is a software to maintain containers. Containers are ready to go images that can run on top of your base os, like virtualisation but in a more direct way, for exemple by sharing the kernel with the os, making it lighter and way more efficient than full virtualisation